The present invention relates to the processing of an anti-reflective coating on a substrate.
In electronic circuit fabrication, an interconnect feature, such as a wiring line or a contact plug, is used to electrically connect electronic features that are formed on a substrate. The interconnect feature is typically formed by depositing on the substrate, stacked layers comprising, for example, a diffusion barrier layer, an electrical conductor layer, and an anti-reflective coating. The diffusion barrier layer reduces the inter-diffusion of underlying substrate materials to the overlying layers, the electrical conductor layer comprises an electrically conducting metal or metal compound, and the anti-reflective coating reduces the reflectivity of the underlying conductor layer to allow more accurate patterning of a mask that may be formed on the stacked layers for etching. After the patterned mask is formed, by for example, photo or electron beam lithographic processes, the unprotected portions of the stacked layer are etched to form a pattern of interconnects on the substrate. A dielectric layer, such as silicon dioxide, may also be deposited over the interconnects for their electrical isolation. The interconnects may also be formed by sequentially depositing these or other materials into contact holes that are etched in the substrate.
In one configuration, the diffusion barrier layer below the conductor layer, includes amongst other layers, a titanium oxide layer. Such a titanium oxide layer is typically formed by sputter depositing elemental titanium metal on the substrate in a PVD chamber, and thereafter, transferring the substrate to an oxidizing chamber to oxidize the titanium by heating it in an oxygen environment to form titanium oxide, as for example, disclosed in U.S. Pat. No. 6,144,097, which is incorporated herein by reference in its entirety. However, it is difficult to control the stoichiometry of the titanium oxide layer formed by this method throughout the thickness of the layer, and often, the oxidized titanium oxide layer can have a variable stoichiometry through its thickness. Thus, it is desirable to find other ways of forming a titanium oxide layer having a more controllable composition.
After forming the diffusion barrier layer, a conductor layer, such as aluminum or copper layer, is deposited on the diffusion barrier layer, to serve as an electrically conducting layer. The conductor layer is typically formed by conventional PVD methods. Then, an anti-reflective coating is formed on the conductor layer, typically by chemical vapor deposition (CVD) and physical vapor deposition (PVD) processes that are sequentially performed in both CVD and PVD chambers, respectively. For example, an anti-reflective coating comprising a titanium metal layer and a titanium nitride layer (TiN), may be formed by sputter depositing the two layers in PVD chambers. Such an anti-reflective coating typically provides a surface reflectivity of about 60% as compared to a 100% reflectivity of a bare silicon wafer. The surface reflectivity may be improved by depositing SiO2 and/or SiON layers over the TiN layer to reduce the surface reflectivity to less than about 10%. However, typically, the SiO2 and SiON layers are deposited by chemical vapor deposition processes performed in CVD chambers. This requires the substrate to be transferred from a PVD chamber to a CVD chamber, which increases processing time and potentially reduces substrate yields through contamination during the transferring step.
A further problem arises from the out-gassing of gaseous species from the chamber walls during the film formation step. The chamber walls may retain species, such a hydrogen gas, from prior processing steps performed in the chamber. Such gaseous species may combine with other gases that are used in the processing step to form undesirable byproducts in the chamber that affect the quality of the film being formed on the substrate or that may result in other adverse effects. For example, out-gassed hydrogen can combine with oxygen to form water vapor which hinders the high vacuum pumping system that exhausts the gases from the chamber.
Thus, it is also desirable to be able to fabricate an anti-reflective coating having a low reflectivity in a sequence of steps that may be performed in a single chamber such as, for example, a PVD chamber, to provide increased process throughput and higher substrate yields. It is further desirable to have an anti-reflective coating having a surface reflectivity of, for example, less than 10% to, for example, improve the accuracy and resolution of lithographic processes that are performed to pattern a mask formed on the substrate. It is also desirable to have an apparatus that can accommodate for the out-gassing of undesirable gaseous species in the chamber.
A method of depositing titanium oxide on a substrate, the method comprising:
(a) placing a substrate in a process zone;
(b) applying a pulsed DC voltage to a target facing the substrate, the target comprising titanium; and
(c) maintaining a sputtering gas at a sub atmospheric pressure in the process zone, the sputtering gas comprising an oxygen-containing gas,
whereby titanium oxide is deposited on the substrate.
A method of sputter depositing material on a substrate in a multi-chamber platform comprising first and second sputtering chambers, the method comprising:
(a) in a diffusion barrier deposition stage, forming a diffusion barrier layer on a substrate;
(b) in a conductor deposition stage, transferring the substrate to a support in the first sputtering chamber, providing a target comprising conductor material facing the substrate, and maintaining an energized sputtering gas at a sub atmospheric pressure in the process zone, whereby conductor material that is sputtered from the target is deposited onto the substrate to form a conductor layer; and
(c) in an anti-reflective coating deposition stage, transferring the substrate to a support in a second sputtering chamber, applying a pulsed DC voltage to a target comprising titanium facing the substrate, and maintaining a sputtering gas at a sub atmospheric pressure in the process zone, the sputtering gas comprising oxygen and argon, whereby titanium that is sputtered from the target combines with the oxygen to form an anti-reflective coating of titanium oxide on the substrate.
A method of sputter depositing a stacked layer on a substrate in a multi-chamber platform comprising a load-lock chamber and first and second sputtering chambers, the method comprising:
(a) placing a plurality of substrates in the load-lock chamber;
(b) in a diffusion barrier deposition stage, forming a diffusion barrier layer on one of the substrates;
(c) in a conductor deposition stage, (i) transferring the substrate to a support in the first sputtering chamber, (ii) providing a target facing the substrate, the target comprising a conductor material, (iii) maintaining an energized sputtering gas at a sub atmospheric pressure in the process zone, whereby conductor material that is sputtered from the target is deposited on the substrate; and
(d) in an anti-reflective coating stage, (i) transferring the substrate to a support in the second sputtering chamber, (ii) providing a target comprising titanium facing the substrate, (iii) applying a pulsed DC voltage to the target, the pulsed DC voltage having a frequency of from about 50 kHz to about 300 kHz and being pulsed so that the voltage is off from about 5% to about 50% of the time of each pulse cycle, and (iv) maintaining a sputtering gas at a sub atmospheric pressure in the process zone, the sputtering gas comprising a volumetric flow ratio of oxygen to argon of from about 4:1 to about 9:1, whereby titanium that is sputtered from the target combines with the oxygen to form an anti-reflective coating of titanium oxide on the substrate.
A sputtering chamber for depositing titanium oxide on a substrate, the chamber comprising:
a substrate support;
a target facing the substrate support, the target comprising titanium;
a pulsed DC source to provide a pulsed DC voltage to the target;
a gas inlet to introduce a sputtering gas into the chamber, the sputtering gas comprising an oxygen-containing gas; and
an exhaust to exhaust the sputtering gas.
A sputtering chamber for depositing titanium oxide on a substrate, the chamber comprising:
a substrate support;
a target facing the substrate support, the target comprising titanium;
a pulsed DC source to apply a pulsed DC voltage to the target;
a sputtering gas supply comprising an oxygen input to receive oxygen from an external source and an argon input to receive argon from another external source, and mass flow controllers adapted to control the oxygen and argon flow rates from the inputs into the chamber;
an exhaust to exhaust gas from the chamber; and
a controller comprising a computer having computer readable program code embodied in a computer readable medium, the computer readable program code comprising:
voltage source program code to operate the pulsed DC source to apply the pulsed DC voltage to the target; and
gas flow program code to operate the mass flow controllers to control the gas flow rates to maintain a volumetric flow ratio of oxygen to argon of from about 4:1 to about 9:1,
whereby titanium that is sputtered from the target and the oxygen combine to deposit titanium oxide on the substrate.
An apparatus for depositing material on a substrate, the apparatus comprising:
a platform that interconnects a plurality of chambers so that a substrate may be transferred from one chamber to another chamber;
a load-lock chamber on the platform to receive a cassette of substrates;
a first sputtering chamber mounted on the platform, the first sputtering chamber comprising (i) a substrate support, (ii) a target facing the substrate support, the target comprising a conductor material, (iii) a gas inlet to provide a gas into the chamber, (iv) a gas energizer to energize the gas, and (v) an exhaust to exhaust the gas, whereby conductor material is sputtered from the target and onto the substrate; and
a second sputtering chamber mounted on the platform, the second sputtering chamber comprising (i) a substrate support, (ii) a target facing the substrate support, the target comprising titanium, (iii) a pulsed DC source to bias the substrate support with a pulsed DC voltage, (iv) a gas inlet to introduce a gas into the chamber, the gas comprising an oxygen-containing gas and argon, and (v) an exhaust to exhaust the gas, whereby titanium that is sputtered from the target and the oxygen-containing gas combine to deposit titanium oxide on the substrate.
A method of depositing titanium oxide on a substrate, the method comprising:
(a) placing a substrate in a process zone;
(b) electrically biasing a target facing the substrate, the target comprising titanium;
(c) introducing a sputtering gas into the process zone, the sputtering gas comprising a first volumetric flow ratio of an oxygen-containing gas and argon;
(d) changing the first volumetric flow ratio to a second volumetric flow ratio;
(e) exhausting the sputtering gas,
whereby multiple layers of titanium oxide are deposited on the substrate.
A sputtering chamber for depositing titanium oxide on a substrate, the chamber comprising:
a substrate support;
a target facing the substrate support, the target comprising titanium;
a voltage source to apply a voltage to the target;
a sputtering gas supply comprising an oxygen input to receive an oxygen-containing gas from an external source and an argon input to receive argon from another external source, and mass flow controllers adapted to control the oxygen-containing gas and argon flow rates from the inputs into the chamber;
an exhaust to exhaust gas from the chamber; and
a controller comprising a computer having computer readable program code embodied in a computer readable medium, the computer readable program code comprising gas flow program code to operate the mass flow controllers to control the gas flow rates to provide a sputtering gas comprising first volumetric flow ratio of oxygen-containing gas to argon for a first time period, and a second volumetric flow ratio of oxygen-containing gas to argon for a second time period,
whereby titanium that is sputtered from the target and the oxygen combine to deposit multiple layers of titanium oxide on the substrate.